# of Cats on Fox Body H-Pipe

[HISSIN50]

Ah Hissin, you're killing me!

Don't take this as gospel, but I've read that the "pre" cats are one ways and that the second is a two way. The pre's are there because they heat up faster and reduce emissions while the car is cold. After market pipes use 2 3-way cats.

Thanks for the reply bud - I was not trying to be a pain. I recently had to jump through hoops with the EPA over this stuff because I have an aftermarket catted pipe (2 total) instead of the stock 4 on one of the stangs.

I have read so many sources of info and I never saw anything definitive. When dealing with this stuff, I had wanted to know exactly what was inside each cat. I thought the same as you, but then one decent source mentioned that the second cat was a 3-way, which surprised me and made me wonder why the first cat was needed (I also thought it was a one way and a two way, as tech was not as good back in the day).

I do appreciate your info.

 

[ALMOST STOCK]

Unless I wrong IHCScoutMan asked

how many catalytic converters come on an OEM H-pipe on a '92 fox body. Or any fox body for that matter.

And I see 4 in that pic....be it pre or af,............... it's just 4... RIGHT?

 

[Lyncher]

Pre= before

 

[StreetStang302]

So the "precats" are 2 out of the 4 cats? right?

 

[StreetStang302]

Anyone willing to answer my question if the "precats" are 2 out of the 4 cats? Well, are they?

 

[HISSIN50]

Anyone willing to answer my question if the "precats" are 2 out of the 4 cats? Well, are they?

I can tell you with 50% certainty.

That is just what we were debating and I really dont know or I would tell ya bud. I want to know too.

 

[Mustang5L5]

To clear it all up: The above picture is correct (with minor differences) for all '86-'2004 'stangs with a factory H-pipe. The pre cats are the 2 small ones right after the header flanges(1 on each side).

96-98 4.6L Mustangs came with 6 cats.

For the '99 model year Ford went back to 4-cat pipes but used up remaining supplies on early '99's.

So some '99 Mustangs have the 6-cat h-pipe while later '99-04's had a 4-cat pipe.

 

[ALMOST STOCK]

Ok... so on the 96-98 4.6L Mustangs with 6 cats, that would that be 4 precats and 2 cats then right?

 

[MyCARneedsHelp]

there were 4 cats on my 88 GT and my 87 GT. They both were simular to the pic ALMOSTSTOCK posted....

 

[89Red5.0]

my 89GT has four. two forward, two aft. kinda crappy b/c i had a custom built cat-back and the fwd stock ones couldnt b replaced/removed w/o a ton more work.

 

[RacEoHolic330]

The first 2 cats near near the header flanges are the pre cats, and as stated before they are there to reduce emissions when the engine isn't running at operating temp.

Those of you with aftermarket catted x or h pipes, you've probably noticed that when you start your car up when the engine is cold the exhaust fumes are really strong for a few minutes. That's because the cats haven't had time to heat up yet and do their job. The pre cats on a stock h-pipe are closer to the engine so they heat up much quicker and, in turn, recuce emissions when the engine is cold.

 

[4G-KDMP]

now i understand.

 

[StreetStang302]

So to clear everything up, when I put my Off-Road H-Pipe on in 2 weeks, there will be no "precats" and no cats at all, right? and for the final question, will someone that honestly 100% knows, answer the following question, the "precats" on my '89 are 2 out of the 4 cats on my stock H-Pipe, right?

 

[Mustang5L5]

Yes, the first 2 closest to the engine are precats and the other 2 are the main converters.

Their function is to control emmissions on cold startup. Cat's work better hot, so by being close to the headers, they warm up faily quickly and begin converting gases right away.

The Main cats take a bit longer to warm up so that is why Ford uses pre-cats.

You can pass emmissions with a aftermarket H-pipe with 2 cats. Just make sure you drive around for a while and get the car faily hot before heading to the inspection station.

2-cat h-pipes will pass inspection. Various states have passed around notices that a Mustang with 2-cats will pass visual if it passes emmissions.

 

[HISSIN50]

So what is inside a 'pre cat'? It sounds like atleast one matrix (it is at least a one-way cat).

FWIW, I just flunked the visual inspection with an aftermarket catted (two 3-way cats) H-pipe. There is nothing steadfast with emissions testing IMHO (other locals with the same pipe pass all the time). Kind of a luck-of- the-draw thing.

 

[StreetStang302]

Yes, the first 2 closest to the engine are precats and the other 2 are the main converters.

Their function is to control emmissions on cold startup. Cat's work better hot, so by being close to the headers, they warm up faily quickly and begin converting gases right away.

The Main cats take a bit longer to warm up so that is why Ford uses pre-cats.

You can pass emmissions with a aftermarket H-pipe with 2 cats. Just make sure you drive around for a while and get the car faily hot before heading to the inspection station.

2-cat h-pipes will pass inspection. Various states have passed around notices that a Mustang with 2-cats will pass visual if it passes emmissions.

Thanx for clearing everything up. Later, Jeff.

 

[ALMOST STOCK]

So what is inside a 'pre cat'? It sounds like atleast one matrix (it is at least a one-way cat).

What I saw when I took this pic of the 'per cat', as I looked down through the pipe I saw a honey comb or very fine looking mess of some sort.

View attachment 504121

 

[HISSIN50]

Almost Stock, Thank you sir. That looks more like a one-way cat than something that is not a cat (the name 'pre-cat' suggests something other than a cat, to me).

 

[ALMOST STOCK]

(the name 'pre-cat' suggests something other than a cat, to me).

That is my thought also.